The present invention relates to a display device, an image display device and an image display method, and more particularly to a display device, an image display device and a display method used for a thin image display device such as a flat panel display.
Heretofore, a liquid crystal display (LCD) device has been widely used as an image display device of an information terminal apparatus such as a personal computer or a portable information terminal (personal digital assistance: PDA) or of a car navigation system. While a liquid crystal display device using TFTs has advantages in that response speed thereof is fast and it can display a clear multicolor moving picture, the liquid crystal display device has disadvantages in that power consumption thereof is high, electric power is required for maintaining an image, a viewing angle thereof is narrow, and so on, because the liquid crystal display device requires an illumination light source such as a backlight and light utilization efficiency of the illumination light source is also low.
Therefore, image display devices according to various methods have been proposed as replacements of the liquid crystal display device. For example, a display device which switches ON/OFF of image display by use of a film boiling phenomenon of liquid has been proposed (for example, refer to JP 05-127603 A and JP 05-127604 A). Moreover, a display device which switches ON/OFF of image display in the manner in which ink is moved by use of electrocapillarity has also been proposed (for example, refer to JP 10-039799 A).
Furthermore, there has also been proposed a display device which switches ON/OFF of image display in the manner in which ink is loaded/unloaded to/from an image display unit by thermally expanding and shrinking ink in segments or mechanically driving diaphragms (for example, refer to JP 2001-042794 A). Still further, there has also been proposed a display device which switches ON/OFF of image display in the manner in which ink is moved by use of electrostatic force (for example, refer to JP 08-254962 A).
However, in each of the image display devices utilizing the film boiling phenomenon of fluid, which are disclosed in JP 05-127603 A and JP 05-127604, when color display is attempted, it is necessary to spread the respective cells of red (R), green (G), and blue (B) or the respective cells of cyan (C), magenta (M), and yellow (Y) in a horizontal direction. Accordingly, each of the image display devices has problems in that the light utilization efficiency is in principle poor and in that contrast of the device is low. Moreover, in the display device disclosed in JP 10-039799 A, the respective types of ink, which correspond to red (R), green (G), and blue (B), are compounded in the same cell, and accordingly, the light utilization efficiency is improved. However, the device involves a problem in that it is difficult to let a desired color come out after rewriting because it is difficult to separate the image into the three colors when the image display is turned off.
Furthermore, according to such a method of thermally expanding or shrinking ink, which is disclosed in JP 2001-042794 A, a thermal expansion coefficient of the ink is low, and accordingly, a volume change of the ink is as small as approximately 2% even if the ink is heated up to 300 K to 350 K. Therefore, when one attempts to secure a predetermined volume change, a considerably large reservoir tank with respect to a volume of the image display unit is necessary, leading to a problem of upsizing of the device. Moreover, according to such a method of mechanically driving the diaphragms, the structure of the device becomes complicated, leading to a problem in that downsizing of the device is inhibited. Furthermore, in the display device disclosed in JP 08-254962 A, the respective color cells corresponding to cyan (C), magenta (M), and yellow (Y) form a stacked structure. Accordingly, in order to set a certain color in a non-display state, ink corresponding to the color must be moved under the other cell. Therefore, there arise a problem of the deterioration of image quality due to step differences occurring in an array of the cells, and a problem of the movement of ink taking a long time and hence low responsiveness.